A number of devices have been known in the machine art for providing intermittent incremental advance by means of a rotating shaft. The output shaft of such devices can mount a working rotating table for direct translation of motion, or other device such as gears for translating the intermittent incremental or indexing rotary shaft motion into a conveyor belt drive or other linear incremental indexing drive. One such device is the well-known Geneva wheel which has harmonic motion and which is usually designed to provide only one angle of incremental advance about its driving shaft axis. The angle is normally non-adjustable. Wear causes problems and tends to cause variation in the incremental advance. Another problem is serious machine damages during jams since this type of mechanism cannot slip in overload condition.
Geneva wheel arrangements are set for a single angular increment of advance. Thus if there are three different increments needed for a particular operation in a factory, three different machines are needed. If one wants to have back ups for each of the machines, three back up spare machines are needed. This severely cuts down versatility and can cause additional expense in certain factory operations. Other devices such as cam mechanisms also provide harmonic motion with the same type of problems as the Geneva drive.
Electro-vacuum and electro-magnetic friction clutch brake systems have been used in the past with a sliding disk operating on a rotating axle to cause stopping and starting of harmonic motion systems. Such systems in the past give slight cumulative variations in incremental advance which causes changes in indexing positions which are substantial over prolonged time periods.